AUSTIN, Texas — Edward Snowden, who leaked classified documents revealing the surveillance activities of the National Security Agency, said technology companies need to take a leadership role in improving encryption tools.

“There’s a technical response that needs to occur,” said Snowden, speaking through a video feed to a packed room of more than 3,000 Monday at the South by Southwest Interactive conference. Technology companies can add layers of security that make it harder for intelligence agencies to scour for data, and can do it faster than new surveillance-oversight laws can be implemented, he said.

Snowden is now a fugitive in Russia to avoid arrest following last year’s release of the documents, which disclosed how global spy agencies collect vast amounts of data about phone calls and online activities. The revelations frayed U.S. relationships with countries such as Brazil and Germany and set off a global debate about whether the government is overstepping its authority and violating privacy to bolster security.

The leaks from Snowden, a former NSA contractor, showed that the United States had been collecting phone records as well as data from companies such as Google, Facebook and Apple. The disclosures made Snowden a hero to some people who want to see government activities reined in, while others, including President Barack Obama, say his actions compromised efforts to combat terrorism.

Agency oversight

Snowden, speaking in front of an image of the U.S. Constitution, said the NSA’s technique of collecting mass amounts of data hasn’t been effective because there aren’t good ways to interpret the material.

“What did we get out of it?” he said. “We got nothing.”

Better oversight of intelligence agencies is needed, Snowden said. Congress has been “cheerleading” instead of acting as a watchdog, he said.

“That’s the biggest failure,” he said.

Chris Soghoian of the American Civil Liberties Union, speaking with Snowden, said there’s inherent tension in having technology companies play a central role because their business models are dependent on using personal information to sell advertising. Technology companies have dramatically improved their security since Snowden’s leaks, he said, because the revelations raised concerns among their users.

“His disclosures have improved Internet security,” Soghoian said.

Privacy theme

Security and privacy have been main themes of South by Southwest this year. Known as the conference that helped catapult Twitter to popularity, the gathering typically focuses on the discovery of new social-networking companies. Instead, this year’s event has focused more on the drawbacks and consequences of sharing personal information online.

Wikileaks founder Julian Assange spoke at the conference Saturday and said the group would soon release a new trove of classified information. He didn’t disclose the timing or the topic of the material because he said he didn’t want to give the subjects a chance to prepare.

Other speakers, including Google chairman Eric Schmidt, have discussed the impact of Snowden’s leaks. Schmidt said the material alerted his company to the fact the U.S. government was intercepting data from Google’s servers. Schmidt said the company has since enhanced its encryption and is “pretty sure” the government can’t access the data. Still, he said the company must comply with court orders for information.

Schmidt said there must be a balance between transparency and security, because the government data being disclosed could put lives at risk. Assange and Snowden’s release of classified information have made them “celebrities,” Schmidt said, and may spawn copycat efforts, increasing the risk for harm if the disclosures aren’t done carefully.

“There’s a real concern about the nature of celebrity driving more and more of these,” he said.